This invention relates generally to gear pumps for use in pumping liquid substances and the like. More specifically, this invention relates to an improved gear pump adapted for rapid and easy adjustment of internal operating clearances without requiring pump disassembly.
Gear pumps in general are well known in the art and typically comprise a matched set of meshing spur gears carried on parallel rotating shafts and mounted generally within a contoured gear pocket or chamber within a pump housing. The pumping gears are rotated together causing their gear teeth to sweep a fluid from a housing inlet port to an outlet port typically at an elevated discharge pressure. Such gear pumps are most commonly used in the prior art for pumping hydraulic fluids and other liquid substances, such as oils, fuels, and the like, frequently at relatively high output pressures.
For optimum performance capacity, gear pumps are designed with relatively close and, in some cases, substantially zero internal operating clearances to prevent significant fluid bypass leakage between the housing inlet and outlet ports. More specifically, as the gear teeth of each pumping gear rotate away from the housing inlet port, the radially outermost tips of the gear teeth move in close running clearance with a respective pair of arcuate pressure faces defined by the gear pump housing and located at relative positions between the inlet and outlet ports. This close running clearance between the gear teeth tips and the pressure faces is designed to prevent significant fluid leakage in the reverse direction from the outlet port to the inlet port, wherein such leakage would have an adverse affect upon pump output pressure. Accordingly, the provision of close running or operating clearances permits gear pump operation at a relatively high output pressure capacity.
One disadvantage encounterend with traditional gear pumps, however, is that they tend to experience significant reductions in output pressure performance capacity in response to component wear. That is, pump operation inherently results over a period of time in mechanical wear especially between the outer tips of the pumping gear teeth and the housing pressure faces. Alternately, such wear can occur rapidly upon ingestion of fluid-entrained grit or upon use to pump caustic or abrasive materials. This wear is accompanies by an increase in the operating clearance between the gear teeth tips and the pressure faces to result, in some instances, in dramatic reductions in output pressure capacity. As one illustrative example, in a gear pump designed for an operating clearance of about 0.001 inch and a design output pressure of about 500 psi, a wear-induced increase in the operating clearance to about 0.005 inch can result in a reduction in output pressure to 50-60 psi.
In the past, upon experiencing a degradation in pump output pressure to a level below a design on rated threshold, it has been necessary to disassemble the gear pump for purposes of rebuilding or repair. Such pump disassembly and overhaul, however, require significant manual labor and skill and further require the gear pump to be removed from service for a significant period of time.
There exists, therefore, a significant need for an improved gear pump capable of providing a fluid output at a relatively high pressure, wherein the pump can be adjusted quickly and easily and preferably from the exterior of the pump to regenerate pump performance in compensation for component wear. The present invention fulfills these needs and provides further related advantages.